Innovated inertia control of DFIG with dynamic rotor speed recovery
Huanjing Lao, Li Zhang, Tong Zhao, Liang Zou
Abstract
High wind power penetration (WPP) is challenging system frequency stability. As a countermeasure, virtual inertia controls are complemented to utilize kinetic energy (KE) stored in wind turbine generator (WTG) for frequency regulation. While without restoration, generation efficiency of WTG will be degraded after inertia contribution. To counter this issue, we propose an inertia control scheme of doubly fed induction generator (DFIG), aiming at achieving dynamic inertia recovery regarding both of KE and DC link energy. An asymmetrical droop control referred to rate of change of frequency (RoCoF) is proposed for KE management. The upper boundary of droop gain is extended to give full play of converter and revised considering system frequency state to counter positive feedback issue induced by reversible gain regulation, which is restricted by KE in store to ensure stable operation as well. The inertial DC energy to cooperate with KE control regarding countering small fluctuations, is improved with an orderly recovery behavior. Case studies are conducted under dynamic wind condition and the results indicate that with proposed scheme, the ability of dynamic inertia recovery is obtained, bringing DFIG higher generation efficiency and more adequate operation margin for sustained regulation. Essentially, the inertial frequency response and fluctuation suppression ability is well maintained.